Mineralisation of organic matter in fined sediments: an experimental approach

Type:

Master Thesis subject (30 ECTS)

programme:

EMBC+

Human activities in the coastal zone have strong effects on the physical environment: beam trawling, dredging and dumping activities, aggregate extraction and the installation of offshore windmill farms can affect the sediment drastically. The effect of these changes is generally investigated through an assessment of how fauna is impacted but this does not provide answers on how the functioning of the ecosystem is affected.
The majority of coastal sediments consist of clean, coarse sands. These sands act as a filter for the water column, where efficient biogeochemical processes result in fast mineralization of organic matter. On several areas on the Belgian part of the North Sea, we observed that these sediments are either covered by finer sediments, or that finer particles are incorporated in the sand matrix. The efficiency of the mineralization processes (process whereby organic material is changed to its anorganic elements) depends on the availability of oxygen in the sediment. Clean sands are characterized by the presence of oxygen in high concentrations, but the “fining” of such sediments can result in decreased oxygen concentrations, and hence in a decreased mineralization efficiency. Within this thesis, a series of experiments will be performed, along an artificially created gradient of fined sediments. The sediments, and fauna, will be incubated in lab-experiments, and organic matter (diatoms) will be added. During the experiments, the student will investigate how the mineralization rates are affected by the “fining” of the sediment. The student will be involved in sampling, setting up and maintenance of highly specialized experiments, and will get in touch with biogeochemical modeling. The thesis contributes to an ongoing project investigating the effect of fining of sediments at the scale of the Southern Bight of the North Sea.